Cssprobe Cli

cssprobe-cli

Runtime CSS probe — inspect layout, scroll, colors, backgrounds, fonts and more in a live browser. Built for both humans and AI agents.

Static + runtime CSS diagnosis for AI agents — pair with cssgraph (the CSS knowledge graph) for the full picture.

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Why cssprobe-cli?

When an AI agent needs to debug CSS — why is this element overflowing, what's the actual rendered layout, is this container scrollable — it can't see the browser. It guesses from static code, missing runtime-only issues like overflow, scroll chains, and containing block hijacks.

cssprobe-cli gives the agent eyes. It opens a real browser, collects computed styles and metrics via injected JavaScript, analyzes them with a confidence model, and returns structured findings — all in one command. The agent asks a question about any selector and gets back the DOM tree, ASCII layout diagram, overflow warnings, and scroll diagnosis without leaving the terminal.

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Installation

For Humans

Copy and paste this prompt to your LLM agent (Claude Code, Cursor, Codex, etc.):

Install and configure cssprobe-cli by following the instructions here:

https://raw.githubusercontent.com/mack-peng/cssprobe-cli/main/docs/guide/installation.md

Or read the Installation Guide, but seriously, let an agent do it. Humans fat-finger configs.

For LLM Agents

Fetch the installation guide and follow it:

curl -s https://raw.githubusercontent.com/mack-peng/cssprobe-cli/main/docs/guide/installation.md

Or install directly:

npm install -g cssprobe-cli

cssprobe-cli skill-install

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How It Works

┌───────────────────────────────────────────────────────────┐

│ AI Agent │ │ │ │ "Is .sidebar overflowing?" │ │ calls: cssprobe-cli inspect .sidebar │ │ │ │ └─────────────────────────────┬─────────────────────────────┘ │ ▼ ┌───────────────────────────────────────────────────────────┐ │ cssprobe-cli daemon │ │ │ │ collector (IIFE) → analyzer (pure) → renderer (md/json) │ │ │ │ │ ▼ │ │ Playwright browser (Chromium) │ │ getBoundingClientRect · getComputedStyle · DOM walk │ └───────────────────────────────────────────────────────────┘

1. Session — open spawns a daemon process managing a browser. Commands connect via Unix socket.
2. Collector — Injected as IIFE into the page. Walks the DOM, reads computed styles, declared values, and element metrics.
3. Analyzer — Pure Node.js functions. Classifies findings with confidence levels (DEFINITE / INDEFINITE / UNVERIFIABLE).
4. Renderer — Outputs Markdown (default) or JSON. Includes ASCII layout diagram, DOM tree, and findings.

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Quick Start

1. Inspect a Page

# Open browser (non-blocking, starts daemon session)

cssprobe-cli open https://getbootstrap.com/docs/5.3/examples/checkout

Inspect with CSS selector

cssprobe-cli inspect .container

Show ASCII layout diagram

cssprobe-cli layout .container

Show only issues/warnings

cssprobe-cli findings .container

Close browser when done

cssprobe-cli close

2. Login-Protected Pages

# Open browser in headed mode

cssprobe-cli open https://mysite.com --headed

User manually logs in...

Save session state for future use

cssprobe-cli state-save --name mysite

Reopen with saved state (no login needed)

cssprobe-cli open https://mysite.com --state state.json --headed

3. JSON Output

cssprobe-cli inspect body --json

cssprobe-cli inspect body --json | jq '.findings[] | {id, confidence, message}'

4. Use as an MCP Server (AI clients)

cssprobe-cli ships an MCP server (stdio), so AI clients call it as a native tool — no shell needed:

cssprobe-cli mcp-install          # auto-detect and configure installed clients

cssprobe-cli mcp-install --target=claude,cursor,codex cssprobe-cli mcp-install --local # write project-scoped config

Manual configuration for any MCP client:

{

"mcpServers": { "cssprobe-cli": { "command": "cssprobe-cli", "args": ["mcp"] } } }

Exposes 10 tools: cssprobe_open, cssprobe_inspect, cssprobe_tree, cssprobe_layout, cssprobe_findings, cssprobe_eval, cssprobe_screenshot, cssprobe_inject_css, cssprobe_close, cssprobe_status. Remove with cssprobe-cli mcp-uninstall.

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Commands

Session Management

CSS Inspection

Inspection commands accept --frame to target an iframe; the default is the main frame.

CSS Injection

Browser

Interaction

click / hover support --nth N (1-based, default first match), --force (skip actionability checks) and --timeout ms. Without --nth, multiple matches fail (strict) to prevent wrong-target clicks.

State

Configuration

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Multi-step Flows

The interaction commands drive a page step by step; run turns a sequence into a versionable script:

cssprobe-cli open https://example.com/editor

cssprobe-cli wait-for .editor-canvas cssprobe-cli click ".layout-switch" --nth 1 cssprobe-cli type ".block-title input" "Hello" --press Enter cssprobe-cli inspect .block-grid --json cssprobe-cli close

For repeatable flows, write a script and run it with one command. The script runs inside the daemon session (full Playwright page access):

// flow.js

export default async ({ page, context, frames, newPage, click, waitFor, type, inspect, screenshot, expect, log }) => { await page.goto('https://example.com/editor', { waitUntil: 'domcontentloaded' }); await waitFor('.editor-canvas', { state: 'visible', timeout: 10000 });

await click('.layout-switch', { nth: 1 }); await waitFor({ js: "() => document.body.dataset.layout === 'two-col'" });

await type('.block-title input', 'Hello', { press: 'Enter', sequential: true, clear: true }); await waitFor({ networkIdle: true });

const { findings } = await inspect('.block-grid', { format: 'json' }); log('findings:', findings.length); await screenshot({ path: './after-layout-switch.png' });

return { findings: findings.length }; };

cssprobe-cli run ./flow.js        # --timeout ms for the whole script (default 300000, 0 = unlimited)

Scripts must default-export an async function receiving the API object: page, context, frames(), newPage(), click, hover, type, waitFor, inspect, screenshot, expect, log. waitFor accepts { state, timeout, frame }. Uncaught page errors are collected into the result envelope as pageErrors. screenshot relative paths resolve against the script's directory; logs (log() and console.*) are collected and returned with the result. On failure the command exits 1, prints the collected logs, and keeps the session alive.

Scripts are executed by the local daemon with full Node privileges — only run trusted scripts.

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Scenario Suites (Regression)

Run repeatable regression cases from a JSON suite: each case opens a fresh browser, executes steps, asserts on saved values, and writes artifacts + an optional JUnit report.

cssprobe-cli scenario run suites/ticket-26571394.json \

--state ~/.cssprobe-cli/states/preprod.json \ --artifacts out/ticket-26571394 \ --junit out/junit.xml

{

"name": "ticket 26571394 preprod", "defaults": { "viewport": { "width": 1280, "height": 800 } }, "cases": [ { "name": "refresh keeps the hash section align